1. Field of the Invention
The present invention relates to an impact detector to detect impact to an article and a packaging container including the impact detector.
2. Description of the Background Art
In the course of transport, it sometimes happens that fragile packaged articles such as precision equipment fall or are dropped due to inappropriate handling, accidents, or the like. The impact of the fall or drop can damage the articles. For this reason, therefore, impact detectors are typically attached to packaged articles to detect whether or not the article has been subjected to impact.
For example, JP-2009-156726-A discloses an impact detector shown in FIG. 16. Referring to FIG. 16, an impact detector 10 is for detecting impact of fall or drop of a packaged article. The impact detector 10 includes a leaf spring 3 and a weight 6, both disposed inside a case 2. The interior of the case 2 and the leaf spring 3 together form a vertical transition path 11, through which the weight 6 moves down when the case 2 is subjected to an impact in a vertical direction as well as lateral transition paths 12 through which the weight 6 moves when the case is subjected to an impact in a direction oblique to the vertical direction. In this known impact detector 10, the leaf spring 3 includes free ends 3a and projections 3b and 3c so that the position of the weight 6 in the vertical transition path 11 can differ depending on the magnitude of the impact. Thus, the impact detector 10 displays an impact history with the position of the weight 6.
In the impact detector 10, when the impact in the vertical direction, that is, the impact from below is relatively small, the weight 6 does not push away the upper projections 3c of the leaf spring 3 from each other and remains at an initial position indicated by a solid line. By contrast, when the impact from below is sufficiently great for the weight 6 to push away the projections 3c from each other, the weight 6 expands the gap between the projections 3c, moves down, and then is caught between the lower projections 3b. When the impact is greater, the weight 6 pushes away the lower projections 3b from each other and moves down to the bottom of the case 2. At that position, the weight 6 is visible through an inspection window formed in a bottom portion of the case 2. Additionally, with the projections 3b, the weight 6 does not move toward the initial position. By contrast, when the packaged article falls in a lateral direction, the weight 6 moves through the lateral transition path 12, beyond a curved portion 1a of the leaf spring 3, and stops below and to the side of the leaf spring 3 in FIG. 16. Thus, the known impact detector 10 detects impact (external force) on the package article in multiple different directions, that is, lateral fall and drop of the packaged article, and provides a record (history) of the impact distinguishable in multiple different directions.
Although the impact detector 10 is configured to detect both the drop and lateral fall of the packaged article and to guide the weight 6 to different positions depending on the type (magnitude and direction) of the impact, it is possible that a complicated combination of magnitude and twist of the external force can generate false reading by the impact detector 10. In other words, it is possible that the weight 6 moves through the lateral transition path 12 even when the packaged article has not fallen in the lateral direction.
In view of the foregoing, the inventors of the present inventions recognize that there is a need for a more accurate impact detector.